Field of the Invention
The invention relates to a light quantity control apparatus such as a shutter or an aperture stop used in a camera, and to an optical apparatus and an image pickup apparatus including the light quantity control apparatus.
Description of the Related Art
Japanese Patent Laid-open No. 2-153334 discloses a spherical shutter in which its shutter blade, which is conventionally formed in a planar shape, is spherically formed so as to reduce diameter of a lens barrel and size of a camera body.
However, in the spherical shutter disclosed in Japanese Patent Laid-open No. 2-153334, multiple bosses about which multiple spherical shutter blades rotate extend toward a center of a spherical body formed by the spherical shutter blades. In other words, each of the bosses in Japanese Patent Laid-open No. 2-153334 extends in a normal direction in which a normal to the spherical body formed by the spherical shutter blades extends. Thus, manufacturing of the spherical shutter including such bosses requires a special working process. In particular, when the spherical shutter is formed by plastic molding using a general mold requires a same number of so-called slide molds as that of the bosses, the slide molds being configured to be slidable in directions in which the bosses extend. This requirement results in a complicated mold structure, a high mold cost and an additional mold maintenance process. In addition, using the slide mold forms a mold parting line, and such a parting line may potentially disturb movement of the shutter blades. Moreover, since a portion molded by using the slide mold only has a shape extending in a direction in which the slide mold slides, a portion desired to be molded which extends in an optical axis direction (direction in which a light flux passes through the shutter) cannot be molded, which makes designing of the shutter difficult.